The robotic garden tools, for example, but not limited to, robotic lawnmowers are widely used for grass cutting applications in a lawn. Typically, a robotic lawnmower is an autonomous robotic tool and uses a battery as the power source. Based on the operating load and duration, there is a need to recharge the battery of the robotic lawnmower periodically. As an autonomous robotic lawnmower work unattended, it is required to find a path to a charging station in case the battery power level falls below a threshold power level during operation.
There are many techniques currently used to find a path to the charging station. A simple way of doing that is, by mounting an antenna on the charging station, so whenever the robotic lawnmower needs to charge its battery it will sense the antenna signal to track back to the charging station. But, the problem with such a system is the limited range of antenna; there is a possibility that the robotic lawnmower may not be able to detect the antenna signal before the battery runs out. This problem is more pronounced in case of large areas to be mowed. Another disadvantage of such a system is the increased complexity and cost of mounting an antenna on the charging station in the vicinity of a charging plate.
For overcoming the above mentioned disadvantage, one or more wires may be laid on the mowing surface. These wires may guide the robotic lawnmower to the charging station. This effectively eliminates the problem of increased time for searching for a charging station; but the problem of permanent tracks on the grass surface may occur. This happens because the robotic lawnmower will take the same path each time it needs to charge its battery.
A solution to the above problem may be following the boundary at larger distance; this eliminates the problem of permanent tracks. But this system too has disadvantage that robotic lawnmower may take a long time to reach the station if it starts from a bad spot. Also, if there are multiple areas to be cut, the linking passage may be small and the technique of following wire at large distances will be ineffective.
Further, in order to enable the lawnmower to pass through a narrow passage, and still follow the boundary at a large distance as possible, the system needs to be tuned and tested carefully in order to make it work as intended. The large distance is limited by the dimension of the narrow passage. Thereby, the installation process of such system is complicated and time-consuming.
Perhaps, an effective way to eliminate the drawbacks associated with the wire system is by using a navigation system, like GPS, for guiding the robotic lawnmower around the mowing area. This type of system is more accurate and also provides flexibility in controlling the overall operation with relative ease. But, the system needs complex circuits and interfaces, which increase the overall complexity and cost of the system.
In light of the foregoing, there is a need for an improved method and system to find a path to a charging station, which will overcome the disadvantages of complex integration, increased cost and permanent tracks on the grass surface.